An epitaxial wafer is obtained by forming an epitaxial film by blowing a source gas onto one of the surfaces of a wafer to be a substrate. Such epitaxial wafers are used for the wide applications of semiconductor devices such as memory devices, logic devices, and imaging devices. It is known that while an epitaxial film is formed on the top surface of such a wafer, a slight source gas reaches the rear surface of the wafer and a deposit is unavoidably formed on an end portion of the rear surface of the wafer. Note that in this specification, as described above, one of the surfaces of a wafer on which an epitaxial film is formed is referred to as “top surface”, whereas the surface opposite to the top surface is referred to as “rear surface”.
In order to improve the integration degree of those semiconductor devices, the flatness of epitaxial wafers is a major factor. Accordingly, there is a demand for epitaxial wafers with high quality and high flatness. In view of the above, for the purpose of reducing the surface roughness of an epitaxial wafer and removing the deposit on the end portion of the rear surface of the wafer, both surfaces of the epitaxial wafer are sometimes polished after the formation of the epitaxial film.
JP 2011-023422 A (PTL 1) describes a technique of determining conditions for polishing an epitaxial wafer that are suitable for the amount of the deposit formed on the end portion of the rear surface of the wafer. The amount of the deposit is determined based on the flatness of the wafer before the formation of the epitaxial film, the flatness of the epitaxial wafer after the formation of the epitaxial film, and the film thickness profile of the epitaxial film. In PTL 1 states that an epitaxial wafer with high flatness can be obtained by polishing an epitaxial wafer under the polishing conditions determined as described above. Accordingly, the technique of PTL 1 is a technique of determining polishing conditions after the formation of an epitaxial film, so that the conditions can be optimized for the epitaxial film having been formed.